In monitoring systems which photograph a moving image by using a camera, a technique for automatically detecting a change (scene change) in a photographed moving image by image processing and saving/accumulating (storing) the image when the change is detected has been put into practical use.
In such systems, generally, a plurality of images which are photographed and accumulated when changes are detected are laid out and displayed in the chronological order together with the photography times.
In addition, a function of browsing live images or images photographed at the time of change detection via a network and executing various kinds of setting including parameters of change detection from a remote site has also been put into practical use.
On the other hand, in a video editing system, a change in scene is detected by image processing, and the scene change time and an image at that time are visually displayed on an editing window.
For example, Japanese Patent Laid-Open No. 11-32301 discloses an image processing apparatus including a GUI (Graphical User Interface) which automatically executes cut detection in video editing software and displays the start image of the same scene.
Japanese Patent Laid-Open No. 9-65287 discloses a moving image feature scene detection apparatus which obtains the same scene on the basis of the color tone, speaker, subtitle, and the like and displays the representative image in the scene.
In the above-described monitoring systems, images at the time of change detection can be displayed in a list in the time-series order. However, the magnitude of the change amount between the images is unknown.
On the other hand, in the video editing systems disclosed in the two patent references, the change time and the first scene or representative image by cut detection are displayed. In this case as well, the magnitude of the change amount between the images is unknown.
If the magnitude of the change amount between the displayed images is unknown, as described above, it is difficult to find the portion with the largest change amount from accumulated images.
In the above-described systems, the parameters may be changed such that only images with large change amounts are accumulated and displayed. In this case, however, an image whose change amount is smaller than the threshold value is not accumulated. Hence, it may be impossible at a high probability to see desired images after image accumulation.
In monitoring systems and, more particularly, monitoring systems which can execute remote monitoring using computer networks, a function called motion detection, change detection, or dynamic detection is essential. These detection functions will be referred to as “motion detection” hereinafter (e.g., Japanese Patent Laid-Open No. 08-297792).
In “motion detection”, a change in image between frames or the motion of an object in image between frames sensed by a video camera is detected by image processing. The user is notified of the detection result on a display device or through an output device such as a loudspeaker.
In use of the motion detection function, it is important to determine the threshold value (sensitivity setting) to set the degree of change in image between frames or the degree of motion of the object in image between frames, which is the criterion for notification to the user. If the detection sensitivity is too low, no invaders can be detected. Conversely, if the sensitivity setting is too high, notification takes place even when it is unnecessary.
In some of the conventional systems, sensitivity setting is so easy that one of several preset levels from low to high sensitivity is selected. Alternatively, it is necessary to designate various parameters as numerical values.
In systems of former type, optimum setting is not always possible in actual operation. In systems of latter type, intuitive setting is impossible, and designation of appropriate set values is difficult in itself.
As described above, in the monitoring systems, the function of automatically obtaining a change in monitoring image by image processing and, upon detecting a change, notifying the user of it or saving/accumulating the image has been put into practical use. Some systems have a function of displaying an image change amount during the progress of motion detection processing and interactively adjusting the sensitivity to set the motion detection sensitivity.
For example, a system in which the user can adjust the detection parameter while observing an indicator that indicates the image change amount is known. In addition, Japanese Patent Laid-Open Nos. 11-032301 and 9-65287 disclose video editing systems which have a function of obtaining a scene change by image processing and visually displaying the scene change time and the image at that time on an editing window.
On the other hand, Japanese Patent Laid-Open No. 9-200768 discloses a method of detecting the motion of an image on the basis of the background difference or inter-frame difference. In this method, an image with a motion and an image without any motion are input to set an optimum sensitivity that should prevent any detection error or detection miss.
With the conventional moving image motion detection function, the detection sensitivity can be set. However, the range of actually settable values is often wide, and the detection sensitivity must be adjusted by trial and error. The video editing systems have the function of displaying the scene start image or representative image by cut detection. However, they have no detection intensity adjustment function in general. In the invention disclosed in Japanese Patent Laid-Open No. 9-200768, an appropriate sensitivity range is presented on the basis of an image with a motion and an image without any motion, thereby reducing the load on the user in setting the sensitivity. However, patent reference 3 discloses no specific interface for input by the user.